The offensive odors given off by rendering plants constitute a problem of long standing and many systems have been proposed to remedy this. A number of these prior art proposals are noted in the U.S. Pat. No. 4,141,702, to deVries, which is incorporated by reference in this application.
U.S. Pat. No. 4,141,702 describes a process for treating offensive vapors by an aqueous spray treatment, the spray droplets being a very small diameter and containing a water soluble oxidizing agent. This system is quite effective in the treatment of vapors having high intensity odor constituents. It has been found that where a processing plant produces vapors having high intensity or concentrated odor constituents and vapors having low intensity or dilute odor constituents, better results are obtained by treating them separately employing different reaction conditions tailored to produce optimum results with each category.
One proposal is to provide two reaction chambers, with the high odor intensity vapor entering into the upper part of a high intensity odor chamber treating zone where it is subjected to a spray treatment. The treated vapor exits the lower portion of the chamber and joins the untreated low intensity odor vapors. The mixed vapors are then led to the upper portion of a low intensity treatment chamber where they are subjected to a fine aqueous spray treatment to remove the odor constituents, and the purified vapors exit via an exhaust stack from the lower portion of the low intensity vapor treatment chamber.
While this configuration provides for the separate treatment of the high and low odor vapors, it is an awkward and unnecessarily complex arrangement. The present invention provides for a simple and more efficient design resulting in improved results and lower cost in construction and operation.
Among the objects of the present invention are:
To provide an improved two-stage system for treating separate vapors produced during any manufacturing or treatment process, such as a processing plant, for example, consisting of high intensity odor-containing vapors and low intensity odor-containing vapors;
to admit the high intensity odor-containing vapors into the upper portion of a treating chamber or tower and subjecting them to an aqueous spray treatment for a relatively long time to remove the odor components;
to incorporate into the aqueous spray an oxidant or acid or bases or suitable mixtures thereof, such as NaOCl or H.sub.2 SO.sub.4 ;
to treat the vapors with a multiple aqueous spray system, in a treating tower, each spray containing a different reagent;
to treat the vapors with a dual aqueous spray system in a treating tower, wherein one spray comprises NaOCl and the other spray comprises H.sub.2 SO.sub.4 ;
to mix the treated vapors from the high intensity odor treatment tower with untreated low intensity odor-containing vapors and leading the mixture of vapors into the bottom of a low intensity odor treating tower;
to subject the mixed vapors to an aqueous spray treatment adjacent the place of entry of the vapors into the low intensity odor treating tower for a relatively shorter time to remove the odor constituents and to remove the treated vapors from the top portion of the tower.
Further objects will become apparent from the specification and claims which follow. SUMMARY OF THE INVENTION
The method of this invention treats the high intensity odor-containing vapors and low intensity odor-containing vapors emanating from a processing plant, or any other plant which produces offensive odors, in two treating towers. The high intensity odor-containing vapors are led into the upper part of a first treatment tower, are treated with aqueous spray(s) containing reactive chemical(s), e.g., an oxidant such as NaOCl, or H.sub.2 SO.sub.4 and withdrawn from the bottom of the first treating tower. The treated vapors, admixed with low intensity odor-containing vapors, are admitted into the bottom of a second treatment tower after being subject to an aqueous spray treatment similar to the first treatment, but with a shorter reaction time and lower droplet concentration. Treated vapors are removed from the top portion of the second treating tower.